I can relate. Teaching tennis has undermined my own "Quiet Eye" habit. I have to continually reinforce the habit of keeping the head still, eyes on the contact point during my forward swing. I'll usually make a point of practicing it during mini-tennis or warmup.

I will continue to do more reinforcement with some shadow swings while waiting for the next point to start. I'm usually good for most of 2 sets. Usually toward the end of the 2nd set or the beginning of the 3rd, as I start to fatigue mentally, the old teaching habit creeps into play and I am looking up too early again. It takes me a while to realize what is happening -- but I get the ship to right itself within the next half set.

If I ever play you, I'll remember to ask for tips on my forehand during the changeovers.